EP4050327A1 - Image sensor structures and method - Google Patents
Image sensor structures and method Download PDFInfo
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- EP4050327A1 EP4050327A1 EP22168476.4A EP22168476A EP4050327A1 EP 4050327 A1 EP4050327 A1 EP 4050327A1 EP 22168476 A EP22168476 A EP 22168476A EP 4050327 A1 EP4050327 A1 EP 4050327A1
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- passivation
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- light
- image sensor
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Definitions
- Image sensor structures may be coupled with such microfluidic devices as flow cells to form a sensor system.
- the sensor system may be, for example, a biosensor system.
- Such sensor systems often utilize high density arrays of nanowells disposed in a top layer of a passivation stack of layers (herein the "passivation stack") of the image sensor structure to perform controlled reaction protocols on analytes disposed within the nanowells.
- analytes such as clusters of DNA segments, nucleic-acid molecular chains, or the like
- an identifiable label such as a fluorescently labeled molecule
- One or more excitation lights may then be directed onto the labeled analytes within the nanowells.
- the analytes may then emit photons of an emissive light, which may be transmitted through the passivation stack and into light guides of the image sensor structure that are associated (e.g., located directly below) with each nanowell.
- each light guide is in direct contact with the bottom surface of the passivation stack, wherein each light guide's top surface receives a significant portion of the emissive light photons transmitted from its associated nanowell.
- the light guides direct the emissive light photons to light detectors disposed within the image sensor structure and associated (e.g., located directly below) with the light guides.
- the light detectors detect the emissive light photons.
- Device circuitry within the image sensor structure then processes and transmits data signals using those detected photons. The data signals may then be analyzed to reveal properties of the analytes. Examples of such reaction protocols include high-throughput DNA sequencing for the health and pharmaceutical industries and more.
- Crosstalk includes emissive light that is transmitted from a nanowell, through the passivation stack, and into a neighboring unassociated light guide and detected by an unassociated light detector.
- Crosstalk contributes to the noise level of the data signals that are processed from the light detectors and its associated device circuitry.
- pitches of nanowell rows e.g., a range of about 1.5 microns or less, or a range of about 1.0 microns or less
- crosstalk may become a dominating factor in noise contribution.
- nanowell size is often reduced to accommodate tighter pitch. As a result, the total number of analytes in each nanowell (and consequently the total available emissive signal from each well) is reduced, further compounding the effect of noise such as crosstalk.
- the present disclosure offers advantages and alternatives over the prior art by providing an image sensor structure for example having crosstalk blocking metal structures disposed in the passivation stack.
- the crosstalk blocking metal structures may include pillars or parallel metal plates. By being disposed within the passivation structure, the crosstalk blocking metal structures significantly reduce crosstalk transmitted within the passivation layer and prior to entering top surfaces of light guides of the image sensor structure.
- An image sensor structure in accordance with one or more aspects of the present disclosure includes an image layer.
- the image layer includes an array of light detectors disposed therein.
- a device stack is disposed over the image layer.
- An array of light guides is disposed in the device stack. Each light guide is associated with at least one light detector of the array of light detectors.
- a passivation stack is disposed over the device stack, comprising a first passivation layer and a first chemical protection layer disposed over the first passivation layer.
- the passivation stack for example includes a bottom surface in direct contact with a top surface of the light guides.
- An array of nanowells is disposed in a top layer of the passivation stack, wherein the contours of the nanowells are formed by a top layer of the passivation stack. Each nanowell is associated with a light guide of the array of light guides.
- a crosstalk blocking metal structure is disposed in the passivation stack. The crosstalk blocking metal structure reduces crosstalk within the passivation stack.
- Another image sensor structure in accordance with one or more aspects of the present disclosure includes an image layer.
- the image layer includes an array of light detectors disposed therein.
- a device stack is disposed over the image layer.
- An array of light guides is disposed in the device stack. Each light guide is associated with at least one light detector of the array of light detectors.
- a passivation stack is disposed over the device stack.
- the passivation stack includes a 1 st passivation layer having a bottom surface in direct contact with a top surface of the light guides.
- the passivation stack also includes a 1 st chemical protection layer disposed over the 1 st passivation layer.
- the passivation stack also includes a 2 nd passivation layer disposed over the 1 st chemical protection layer and a 2 nd chemical protection layer disposed over the 2 nd passivation layer.
- An array of nanowells is disposed in a top layer of the passivation stack. Each nanowell is associated with a light guide of the array of light guides.
- a method of forming an image sensor structure in accordance with one of more aspects of the present disclosure includes disposing a device stack over an image layer.
- the image layer includes an array of light detectors disposed therein.
- An array of light guide apertures is etched into the device stack.
- An array of light guides is formed in the light guide apertures.
- Each light guide is associated with at least one light detector of the array of light detectors.
- a 1 st passivation layer is disposed over the array of light guides, such that a bottom surface of the 1 st passivation layer is in direct contact with a top surface of the light guides.
- a 1 st chemical protection layer is disposed over the 1 st passivation layer.
- the 1 st chemical protection layer and 1 st passivation layer are included in a passivation stack.
- An array of nanowells is formed in a top layer of the passivation stack, with the contours of the nanowells formed by the top layer of the passivation stack. Each nanowell is associated with a light guide of the array of light guides.
- a crosstalk blocking metal structure disposed within the passivation stack. The crosstalk blocking metal structure reduces crosstalk within the passivation stack.
- Examples provided herein relate to image sensor structures and methods of making the same. More specifically, examples provided herein relate to image sensor structures having crosstalk blocking metal structures disposed within a passivation stack of the image sensor structures.
- FIG. 1 illustrates a sensor system having one type of image sensor structure disposed therein.
- FIGS. 2-5 illustrate various examples of image sensor structures in accordance with the present disclosure.
- FIGS. 6-16 illustrate various examples of methods of making image sensor structures in accordance with the present disclosure.
- an example sensor system 10 (which, in this example, is a biosensor system 10) includes a flow cell 12 bonded to an image sensor structure 14.
- the flow cell 12 of the biosensor system 10 includes a flow cell cover 16 affixed to flow cell sidewalls 18.
- the flow cell sidewalls 18 are bonded to a top layer 22 of a passivation stack 24 of the image sensor structure 14 to form a flow channel 20 therebetween.
- the top layer 22 of the passivation stack 24 includes a large array of nanowells 26 disposed thereon.
- Analytes 28 (such as DNA segments, oligonucleotides, other nucleic-acid chains or the like) may be disposed within the nanowells 26.
- the flow cell cover includes an inlet port 30 and an outlet port 32 that are sized to allow fluid flow 34 into, through and out of the flow channels 20.
- the fluid flow 34 may be utilized to perform a large number of various controlled reaction protocols on the analytes 28 disposed within the nanowells 26.
- the fluid flow 34 may also deliver an identifiable label 36 (such as a fluorescently labeled nucleotide molecule or the like) that can be used to tag the analytes 28.
- the image sensor structure 14 of the biosensor 10 includes an image layer 40 disposed over a base substrate 38.
- the image layer 38 may be a dielectric layer, such as SiN and may contain an array of light detectors 42 disposed therein.
- a light detector 42 as used herein may be, for example, a semiconductor, such as a photodiode, a complementary metal oxide semiconductor (CMOS) material, or both.
- CMOS complementary metal oxide semiconductor
- the light detectors 42 detect light photons of emissive light 44 that is emitted from the fluorescent labels 36 attached to the analytes 28 in the nanowells 26.
- the base substrate 38 may be glass, silicon or other like material.
- a device stack 46 is disposed over the image layer 40.
- the device stack 46 may contain a plurality of dielectric layers (not shown) that contain various device circuitry 48 which interfaces with the light detectors 42 and process data signals using the detected light photons.
- Each light guide 50 is associated with at least one light detector 42 of the array of light detectors.
- the light guide 50 may be located directly over its associated light detector.
- the light guides 50 direct photons of emissive light 44 from the fluorescent labels 36 on the analytes 28 disposed in the nanowells 26 to their associated light detectors 42.
- the protective liner layer 56 may be composed of a silicon nitride (SiN) and lines the inside walls of the light guides 50.
- the light shield layer 52 may be composed of tungsten (W) and attenuates emissive light 44 and excitation light 58 transmitted into the device stack 46.
- the anti-reflective layer 54 may be composed of silicon oxynitride (SiON) and be used for photolithographic patterning of a metal layer underneath.
- the passivation stack 24 is disposed over the device stack 46.
- the passivation stack 24 includes a bottom surface 60 that is in direct contact with a top surface 62 of the light guides 50.
- the passivation stack 24, may include a passivation layer 64 and a chemical protection layer 66 (which in this case is the top layer 22 of the passivation stack 24).
- the passivation layer 64 may be composed of SiN and include the bottom surface 60 of the passivation stack 24.
- the chemical protection layer 66 may be composed of a tantalum pentoxide (Ta 2 O 5 ) and may be the top layer 22 of the passivation stack 24.
- the array of nanowells 26 is also disposed in the top layer 22 of the passivation stack 24, wherein each nanowell 26 is associated with a light guide 50 of the array of light guides.
- each nanowell 26 may be located directly above an associated light guide 50, such that most of the photons of emissive light 44 that enters the top surface 62 of each light guide 50 is generated from within that light guide's associated nanowell 26.
- excitation light 58 is radiated onto the analytes 28 in the nanowells 26, causing the labeled molecules 36 to fluoresce emissive light 44.
- the majority of photons of emissive light 44 may be transmitted through the passivation stack 24 and enter the top surface 62 of its associate light guide 50.
- the light guides 50 may filter out most of the excitation light 58 and direct the emissive light 44 to an associated light detector 42 located directly below the light guide 50.
- the light detectors 42 detect the emissive light photons.
- the device circuitry 48 within the device stack 46 then process and transmits data signal using those detected photons.
- the data signal may then be analyzed to reveal properties of the analytes.
- some photons of emissive light from one nanowell may be inadvertently transmitted through the passivation stack 24 to a neighboring unassociated light guide 50 to be detected as unwanted crosstalk in an unassociated light detector 42. This crosstalk contributes to noise in the data signals.
- nanaowells for example, nanowells with a pitch of about 1.5 microns or smaller, or more so with a pitch of about 1.25 microns or smaller, and even more so with a pitch of about 1 micron or smaller
- such crosstalk may significantly increase noise levels associated with the data signals.
- nanowell size is often reduced to accommodate tighter pitch.
- the total number of analytes in each nanowell and consequently the total available emissive signal from each well
- the more an image sensor structure is scaled down the more desirable it becomes to reduce crosstalk that is transmitted within the passivation stack 24.
- crosstalk shields are disposed in its device stack 46, which is located below its passivation stack 24.
- the crosstalk shields are used to reduce crosstalk that leaks out of its light guide 50 and is transmitted through its device stack 46 to another light guide 50.
- These crosstalk shields do not reduce crosstalk that is transmitted through its passivation stack 24 and into the top surface 62 of its light guides 50.
- the crosstalk shields of this contrasting example are different from the examples provided herein.
- FIG. 2 a cross-sectional side view of an example of an image sensor structure 100 having crosstalk blocking metal structures 102 in a passivation stack 104 of the image sensor structure 100 is illustrated.
- the crosstalk blocking metal structures 102 may be any appropriate shape, but in this example, they are in the form of metal pillars 106.
- the term "pillar", as used herein, includes structures that extend from a bottom surface to a top surface of a layer in a passivation stack.
- the metal pillars 106 in FIG. 2 extend from the bottom surface 140 of the 1 st passivation layer 142 to a top surface of the 1 st passivation layer 142 within passivation stack 104.
- the image sensor structure 100 may be bonded to a flow cell to form a sensor system similar to that of the sensor system 10 in FIG. 1 .
- the sensor system may be, for example, a biosensor system.
- the image sensor structure 100 includes an image layer 108 disposed over a base substrate 110.
- the base substrate 110 may comprise glass or silicon.
- the image layer 108 may comprise a dielectric layer, such as SiN.
- a light detector 112 is disposed within the image layer 108.
- a light detector 112 as used herein may be, for example, a semiconductor, such as a photodiode, a complementary metal oxide semiconductor (CMOS) material, or both.
- the light detectors 112 detect light photons of emissive light 114 that are emitted from fluorescent labels 116 attached to analytes 118 in nanowells 120 disposed in a top layer 122 of the passivation stack 104.
- the fluorescent labels 116 are made to fluoresce by an excitation light 124 during various controlled reaction protocols.
- a device stack 126 is disposed over the image layer.
- the device stack 126 may contain a plurality of dielectric layers (not shown) that contain various device circuitry 128 which interfaces with the light detectors 112 and process data signals using the detected light photons of emissive light 114.
- Each light guide 130 is associated with at least one light detector 112 of the array of light detectors.
- a light guide 130 may be located directly over its associated light detector112.
- the light guides 130 direct photons of emissive light 114 from the fluorescent labels 116 on the analytes 118 disposed in the nanowells 120 to their associated light detectors 112.
- a light shield layer 134 may be composed of a dielectric material, such as silicon nitride (SiN) or other similar materials, and lines the inside walls of the light guides 130.
- the light shield layer 134 may be composed of a transition material, such as tungsten (W) or other similar materials, and attenuates emissive light 114 and excitation light 124 transmitted into the device stack 126.
- the anti-reflective layer 136 may be composed of an anti-reflective compound, such as silicon oxynitride (SiON), or other similar materials and used for photolithographic patterning of a metal layer underneath.
- the passivation stack 104 is disposed over the device stack 126.
- the passivation stack 104 includes a bottom surface 140 that is in direct contact with the top surface 132 of the light guides 130.
- the passivation stack 104 may include any number of layers of material appropriate to transmit emissive light 114.
- the passivation stack 104 includes a first (1 st ) passivation layer 142 and a 1 st chemical protection layer 144.
- the 1 st passivation layer 142 may be composed of SiN and include the bottom surface 140 of the passivation stack 104.
- the 1 st chemical protection layer 144 may be composed of a transition metal oxide, such as tantalum pentoxide (Ta 2 O 5 ) or other similar materials, and be the top layer 122 of the passivation stack 104.
- An array of nanowells 120 is also disposed in the top layer 122 of the passivation stack 104, wherein each nanowell 120 is associated with a light guide 130 of the array of light guides.
- each nanowell 120 may be located directly above an associated light guide 130, such that most of the photons of emissive light 114 that enters the top surface 132 of each light guide 130 is generated from within that light guide's associated nanowell 120.
- the crosstalk blocking metal structures 102 are disposed in the passivation stack 104, wherein the crosstalk blocking metal structures 102 may reduce crosstalk within the passivation stack 104.
- the crosstalk blocking metal structures 102 may be any appropriate shape, but in this example, they are in the form of metal pillars 106.
- the crosstalk blocking metal structures 102 may be disposed in any appropriate location within the passivation stack 104, but in this example, they are disposed solely in the 1 st passivation stack 142 and between the nanowells 120.
- the crosstalk blocking metal structure 102 may be composed of such metals as, for example, tantalum (Ta), tungsten (W), aluminum (Al) or copper (Cu).
- the crosstalk blocking metal structures 102 may reduce crosstalk that is transmitted through the passivation stack 104 by any appropriate process.
- the crosstalk blocking metal structures 102 may be composed of a material that absorbs the emissive light or blocks the emissive light at a given emissive light frequency.
- the crosstalk blocking metal structures 102 may have a geometric shape and placement within the passivation stack 104 that enables the crosstalk blocking metal structures 102 to direct emissive light 114 away from the top surfaces 140 of the light guides 130.
- each nanowell 120 receives analytes 118 that are tagged with a fluorescent molecular label 116, which generates emissive light 114 in response to an excitation light 124.
- Photons of the emissive light 114 are transmitted from a nanowell 120, through the passivation stack, and into the top surface 140 of an associated light guide 130, which may be located directly below the nanowell 120.
- the photons of emissive light 114 are then guided by the associated light guide 130 to an associated light detector 112, which may be located directly below the light guide 130.
- the associated light detectors 112 detect the photons of emissive light 114.
- device circuitry 128 is integrated with the light detectors 112 to process the detected emissive light photons and provide data signals using the detected emissive light photons.
- the crosstalk blocking metal structures 102 may significantly reduce the number of photons of emissive light 114 that may become crosstalk.
- the reduction may be at least about 5% (e.g., at least about 20%, 30%, 40%, 50%, 60%, or more). In more examples, the reduction is between about 5% to about 50%, such as between 10% and 30%. Other values are also possible.
- the crosstalk blocking metal structures 102 reduce the number of emissive light photons that may otherwise be transmitted from a nanowell 120 to an unassociated neighboring light guide 130 and detected by an unassociated light detector 120 as crosstalk. Since such crosstalk may contribute to the noise level of the data signals, the noise level of the data signals is significantly reduced.
- FIG. 3 a cross-sectional side view of another example of an image sensor structure 200 having crosstalk blocking metal structures 102 in the form of pillars 202 is illustrated.
- the image sensor structure 200 is similar to image sensor structure 100 wherein like features have been labeled with like reference numbers.
- the passivation stack 104 of image sensor structure 200 includes four layers. Those four layers include:
- the four layers 142, 144, 204, 206 of the passivation stack 104 may provide certain advantages over the two layers 142, 144 of the passivation stack 104 (i.e., a two layer passivation stack) of image sensor 100. Those advantages may include, without limitation:
- the bottom surface 140 of the 1 st passivation layer 142 is still the bottom surface of the passivation stack 104 and is in direct contact with the top surface 132 of the light guides 130.
- the top layer 122 of the passivation stack 104 is now the 2 nd chemical protection layer 206.
- the nanowells 120 are disposed in the 2 nd chemical protection layer 206.
- the composition of the 2 nd passivation layer 204 and 2 nd chemical protection layer 206 may be the same as, or similar to, the composition of the 1 st passivation layer 142 and the 1 st chemical protection layer 144 respectively.
- the 2 nd passivation layer 204 may be composed of SiN and 2 nd chemical protection layer 206, may be composed of a tantalum pentoxide (Ta 2 O 5 ).
- the crosstalk blocking metal structure 102 of image sensor structure 200 includes the metal pillars 202.
- the metal pillars 202 are disposed in the 1 st passivation layer 104 and are located between the nanowells 120.
- FIG. 4 a cross-sectional side view of another example of an image sensor structure 300 having crosstalk blocking metal structures 102 in the form of pillars 202 is illustrated.
- the image sensor structure 300 is similar to image sensor structures 100 and 200 wherein like features have been labeled with like reference numbers.
- the passivation stack 104 of image sensor structure 300 is the same as, or similar to, the passivation stack of image sensor structure 200 and also includes four layers. Those four layers include:
- the bottom surface 140 of the 1 st passivation layer 142 is still the bottom surface of the passivation stack 104 and is in direct contact with the top surface 132 of the light guides 130.
- the top layer 122 of the passivation stack 104 is the 2 nd chemical protection layer 206.
- the nanowells 120 are disposed in the 2 nd chemical protection layer 206.
- the crosstalk blocking metal structure 102 of image sensor structure 300 includes the metal pillars 302.
- the metal pillars 302 extend from the bottom surface 140 of the 1 st passivation layer 142 to a top surface 304 of the 2 nd passivation layer 204.
- the metal pillars are also disposed between the nanowells 120.
- FIG. 5 a cross-sectional side view of another example of an image sensor structure 400 having crosstalk blocking metal structures 102 in the form of parallel metal layers 402 is illustrated.
- the image sensor structure 400 is similar to image sensor structures 100, 200 and 300 wherein like features have been labeled with like reference numbers.
- the passivation stack 104 of image sensor structure 400 is the same as, or similar to, the passivation stack of image sensor structure 200 and 300 and also includes four layers. Those four layers include:
- the bottom surface 140 of the 1 st passivation layer 142 is still the bottom surface of the passivation stack 104 and is in direct contact with the top surface 132 of the light guides 130.
- the top layer 122 of the passivation stack 104 is the 2 nd chemical protection layer 206.
- the nanowells 120 are disposed in the 2 nd chemical protection layer 206.
- the crosstalk blocking metal structure 102 of image sensor structure 400 includes the parallel metal layers 402.
- the parallel metal layers 402 are disposed in the 2 nd passivation layer 204 and between the nanowells 120.
- the parallel metal layers 402 may be disposed in the 1 st passivation layer 142 and between the nanowells 120 as well.
- the geometric shape and placement of the parallel metal layers 402 enable these particular crosstalk blocking metal structures 102 to direct crosstalk emissive light in a direction that is relatively parallel to the metal layers 402 and away from unassociated light detectors 112. Additionally, the composition of the parallel metal layers 402 enables these particular crosstalk blocking metal structures 102 to absorb such crosstalk emissive light.
- FIGS. 6-15 the following figures illustrate various methods of making the image sensor structures 100, 200, 300 and 400.
- FIG. 6 a cross sectional side view of an example of image sensor structure 100 at an intermediate stage of manufacture is illustrated.
- the image layer 108 is disposed over the base substrate 110.
- the image layer includes the array of light detectors 112 disposed therein.
- the image layer 108 can be disposed over the base substrate 110 using deposition techniques, such as chemical vapor deposition (CVD) or physical vapor deposition (PVD).
- CVD chemical vapor deposition
- PVD physical vapor deposition
- the multiple dielectric layers (not shown) of the device stack 126, with its associated device circuitry, can also be disposed over the image layer 108 using deposition techniques.
- the light shield layer 134 and the anti-reflective layer 136 may thereafter be disposed over the device stack 126 using any suitable deposition techniques, such as CVD, PVD, atomic layer deposition (ALD) or electro-plating.
- an array of light guide apertures 150 are etched into the device stack. This may be done using any suitable etching processes, such as an anisotropic etching process, such as reactive ion etching (RIE).
- An etching process in this disclosure may include patterning, such as lithographic patterning.
- the protective liner layer 136 can then be disposed over the entire image sensor structure 100, including the sidewalls 152 and bottom 154 of the apertures 150. This may be done using any suitable deposition techniques, such as CVD, PVD or ALD.
- a light guide layer 156 is disposed over the entire structure 100 to fill the apertures 150.
- the light guide layer may be composed of an organic filter material that is capable of filtering out the known wavelengths of excitation light 124 and transmitting through known wavelengths of emissive light 114.
- the light guide layer 156 may be composed of custom formulated dye molecules arranged in a high index polymer matrix.
- the light guide layer 156 is thereafter planarized down to form the light guides 130, wherein the top surfaces 132 of the light guides 130 are substantially level with the top surface of the protective liner layer 138. This may be done using any suitable polishing technique, such as a chemical mechanical polishing (CMP) process. Once polished down, the overall top surface of the image sensor structure 100 is substantially flat.
- CMP chemical mechanical polishing
- the light guides 130 are thereafter recessed down into the light guide apertures 150, wherein each light guide 130 is associated with at least one light detector 112 of the array of light detectors. This can be done with a timed etching process that recesses the light guide layer 156 down at a given rate for a known amount of time.
- the light guides 130 When the etching process is finished, the light guides 130 have been recessed into the light guide apertures 150 such that upper portions 158 of inner side walls 152 of the light guide apertures 150 are exposed. Additionally, the top surfaces 132 of the light guides 130 are recessed to a predetermined depth below a top opening 160 of the light guide apertures 150.
- the 1 st passivation layer 142 is disposed over the array of light guides 130, such that the bottom surface 140 of the 1 st passivation layer 142 is in direct contact with the top surface 132 of the light guides 130.
- the 1 st chemical protection layer 144 can then be disposed over the 1 st passivation layer 142. Both of these processes may be done by CVD or PVD.
- the 1 st chemical protection layer 144 and 1 st passivation layer 142 form at least a portion of the passivation stack 104.
- the array of nanowells 120 may be formed in the top layer 122 of the passivation stack 104 at an appropriate point in the process flow. Each nanowell 120 is associated with a light guide 130 of the array of light guides.
- the nanowells 120 may be formed by disposing the 1 st passivation layer 142 such that it conforms to the upper portions 158 of the inner side walls 152 of the light guide apertures 150. This may be done by CVD, PVD or ALD. Accordingly, the contour of the 1 st passivation layer 142 forms the array of nanowells 120 in the 1 st passivation layer such that each nanowell is associated, and selfaligned, with a single light guide 130.
- crosstalk blocking metal structures 102 can be disposed within the passivation stack 104 at an appropriate point in the process flow. Each crosstalk blocking metal structure 102 may reduce crosstalk within the passivation stack 104.
- the crosstalk blocking structures may be formed as metal pillars 106 by lithographically etching pillar cavities 162 into the 1 st passivation layer 142 such that the pillar cavities 162 are disposed between the nanowells 120. This may be done by a RIE process.
- the metal pillars 106 may then be disposed within the pillar cavities 162. This may be done by a metal plating process. Later any overflow caused by the plating process may be removed by a chemical mechanical polishing (CMP) process.
- CMP chemical mechanical polishing
- the 1 st chemical protection layer 144 may be disposed over the 1 st passivation layer 142 to complete the formation of image sensor structure 100.
- the 1 st chemical protection layer 144 may be disposed using CVD, PVD or ALD.
- FIG. 11 a cross sectional side view of an example of image sensor structure 200 at an intermediate stage of manufacture is illustrated.
- This example of the process flow of image sensor structure 200 is the same as, or similar to, the example of the process flow of image sensor 100 up to and including the process flow disclosed with regards to FIG. 8 . Therefore, at this stage of the process flow, the top surface 132 of the light guides 130 are substantially level with the top surface of the protective liner layer 138. Therefore, the overall top surface of the image sensor structure 200 is substantially flat.
- the 1 st passivation layer 142 is disposed over the structure 200, such that the bottom surface 140 of the 1 st passivation layer 142 is in direct contact with the top surface 132 of the light guides 130.
- This 1 st passivation layer 142 of structure 200 provides a substantially level upper surface 208 of the 1 st passivation layer 142. This may be done by CVD or PVD.
- the metal pillars 202 may then be disposed into the 1 st passivation layer 142. This can be done by first etching pillar cavities 210 into the 1 st passivation layer 142. This may be done using a RIE process. The metal pillars 202 may then be disposed within the pillar cavities 210 using CVD, PVD or electro-plating. Any overflow caused by the deposition of the metal pillars 202 into the pillar cavities 210 may later be removed by a chemical mechanical polishing (CMP) process.
- CMP chemical mechanical polishing
- the 1 st chemical protection layer 144 may be disposed over the relatively flat upper surface 208 of the 1 st passivation layer 142. This may be done by CVD, PVD or ALD.
- the 2 nd passivation layer 204 is disposed over the 1 st chemical protection layer 144. This may be done using any suitable deposition technique, such as CVD, PVD or ALD.
- Nanowells 120 can then be formed into the 2 nd passivation layer 204. This can be done by lithographically patterning and etching the nanowells 120 into the 2 nd passivation layer 204.
- the 2 nd chemical protection layer 206 is disposed over the 2 nd passivation layer 204 to complete the formation of the image sensor structure 200.
- This may be done by using any suitable deposition technique, such as CVD, PVD or ALD.
- the deposition process conforms the 2 nd chemical protection layer 206 to the contours of the nanowells 120 in the 2 nd passivation layer 204, therefore forming the nanowells 120 in the 2 nd chemical protection layer 206.
- the 2 nd chemical protection layer 206, the 2 nd passivation layer 204, the 1 st chemical protection layer 144 and the 1 st passivation layer 142 are all included in the passivation stack 104 of the image sensor structure 200.
- FIG. 13 a cross sectional side view of an example of image sensor structure 300 at an intermediate stage of manufacture is illustrated.
- This example of the process flow of image sensor structure 300 is the same as, or similar to, the example of the process flow of image sensor 100 up to and including the process flow disclosed with regards to FIG. 8 . Therefore, at this stage of the process flow, the top surface 132 of the light guides 130 are at least substantially level with the top surface of the protective liner layer 138. Therefore, the overall top surface of the image sensor structure 300 is substantially flat.
- the 1 st passivation layer 142 is disposed over the structure 300, such that the bottom surface 140 of the 1 st passivation layer 142 is in direct contact with the top surface 132 of the light guides 130.
- This 1 st passivation layer 142 of structure 300 provides a substantially level upper surface 208 of the 1 st passivation layer 142. This may be done by any suitable deposition technique, such as CVD or PVD.
- the 1 st chemical protection layer 144 may be disposed over the relatively flat upper surface 208 of the 1 st passivation layer 142. Then the 2 nd passivation layer 204 may be disposed over the 1 st chemical protection layer 144. Both of these layers 144, 204 may be disposed using any suitable deposition technique, such as CVD, PVD or ALD.
- the metal pillars 302 (which are the crosstalk blocking metal structures 102 of image sensor structure 300) may then be disposed into the 2 nd passivation layer 204, the 1 st chemical protection layer 144 and the 1 st passivation layer 142. This can be done by first etching pillar cavities 306 into the 1 st and 2 nd passivation layers 142, 204 and into the 1 st chemical protection layer 144. This may be done using a RIE process.
- the metal pillars 302 may then be disposed within the pillar cavities 306 using any suitable deposition technique, such as CVD, PVD or electro-plating. Any overflow caused by the deposition of the metal pillars 302 into the pillar cavities 306 may later be removed by any suitable polishing technique, such as a chemical mechanical polishing (CMP) process.
- CMP chemical mechanical polishing
- nanowells 120 can then be formed into the 2 nd passivation layer 204. This can be done by lithographically patterning and etching the nanowells 120 into the 2 nd passivation layer 204.
- the 2 nd chemical protection layer 206 is disposed over the 2 nd passivation layer 204 to complete the formation of the image sensor structure 300. This may be done by CVD, PVD or ALD.
- the deposition process conforms the 2 nd chemical protection layer 206 to the contours of the nanowells 120 in the 2 nd passivation layer 204, therefore forming the nanowells 120 in the 2 nd chemical protection layer 206.
- the 2 nd chemical protection layer 206, the 2 nd passivation layer 204, the 1 st chemical protection layer 144 and the 1 st passivation layer 142 are all included in the passivation stack 104 of the image sensor structure 300.
- FIG. 15 a cross sectional side view of an example of image sensor structure 400 at an intermediate stage of manufacture is illustrated.
- This example of the process flow of image sensor structure 400 is the same as, or similar to, the example of the process flow of image sensor 100 up to and including the process flow disclosed with regards to FIG. 8 . Therefore, at this stage of the process flow, the top surface 132 of the light guides 130 are substantially level with the top surface of the protective liner layer 138. Therefore, the overall top surface of the image sensor structure 400 is substantially flat.
- the 1 st passivation layer 142 is disposed over the structure 400, such that the bottom surface 140 of the 1 st passivation layer 142 is in direct contact with the top surface 132 of the light guides 130.
- This 1 st passivation layer 142 of structure 400 provides a substantially level upper surface 208 of the 1 st passivation layer 142. This may be done by using any suitable deposition technique, such as CVD or PVD.
- the 1 st chemical protection layer 144 may be disposed over the relatively flat upper surface 208 of the 1 st passivation layer 142. This may be done by using any suitable deposition technique, such as CVD, PVD or ALD.
- a first parallel metal layer 402A (which is one of the crosstalk blocking metal structures 102 of the image sensor structure 400) may be disposed over the 1 st chemical protection layer 144.
- Metal layer 402A may be disposed by using any suitable deposition technique, such as CVD, PVD, ALD or electro-plating.
- the 2 nd passivation layer 204 may be disposed over the first metal layer 402A. This may be done by using any suitable deposition technique, such as CVC or PVD.
- a second parallel metal layer 402B may be disposed over the 2 nd passivation layer 204 such that it is parallel to the first parallel metal layer 402A. This may be done by using any suitable deposition technique, such as CVD, PVD, ALD or electro-plating.
- nanowells 120 can then be formed into the 2 nd passivation layer 204, and into the parallel metal layers 402A, 402B. This may be done by lithographically patterning and etching the nanowells 120 into the 2 nd passivation layer 204 and the parallel metal layers 402A, 402B.
- the 2 nd chemical protection layer 206 is disposed over the 2 nd passivation layer 204 to complete the formation of the image sensor structure 400.
- This may be done by using any suitable deposition technique, such as CVD, PVD or ALD.
- the deposition process conforms the 2 nd chemical protection layer 206 to the contours of the nanowells 120 in the 2 nd passivation layer 204, therefore forming the nanowells 120 in the 2 nd chemical protection layer 206.
- the 2 nd chemical protection layer 206, the 2 nd passivation layer 204, the 1 st chemical protection layer 144 and the 1 st passivation layer 142 are all included in the passivation stack 104 of the image sensor structure 400.
- the image sensor structures 100, 200, 300, 400 may be disposed onto a printed circuit board (not shown).
- any one of the image sensor structures 100, 200, 300, 400 may be bonded, by using any suitable bonding technique, to a flow cell (like flow cell 12) to form a sensor system (like, for example, biosensor system 10).
- the sensor system may be bonded, by using any suitable bonding technique, to a printed circuit board. This may be done by, for example, adhesive bonding.
Abstract
Description
- Image sensor structures may be coupled with such microfluidic devices as flow cells to form a sensor system. The sensor system may be, for example, a biosensor system. Such sensor systems often utilize high density arrays of nanowells disposed in a top layer of a passivation stack of layers (herein the "passivation stack") of the image sensor structure to perform controlled reaction protocols on analytes disposed within the nanowells.
- In an example of such a reaction protocol, analytes (such as clusters of DNA segments, nucleic-acid molecular chains, or the like) that are disposed in a nanowell array of an image sensor structure may be tagged with an identifiable label (such as a fluorescently labeled molecule) that is delivered to the analytes via fluid flow through a flow cell. One or more excitation lights may then be directed onto the labeled analytes within the nanowells. The analytes may then emit photons of an emissive light, which may be transmitted through the passivation stack and into light guides of the image sensor structure that are associated (e.g., located directly below) with each nanowell.
- A top surface of each light guide is in direct contact with the bottom surface of the passivation stack, wherein each light guide's top surface receives a significant portion of the emissive light photons transmitted from its associated nanowell. The light guides direct the emissive light photons to light detectors disposed within the image sensor structure and associated (e.g., located directly below) with the light guides. The light detectors detect the emissive light photons. Device circuitry within the image sensor structure then processes and transmits data signals using those detected photons. The data signals may then be analyzed to reveal properties of the analytes. Examples of such reaction protocols include high-throughput DNA sequencing for the health and pharmaceutical industries and more.
- As the need for increasing the throughput of reaction protocols continuously grows, so does the need to continuously reduce the size of nanowells in nanowell arrays in an image sensor structure and, therefore, increase the number of nanowells in the nanowell arrays. As pitch (i.e., the distance between repetitive structures in a semiconductor structure) between rows of nanowells in an array becomes increasing smaller, crosstalk becomes an increasingly significant factor.
- Crosstalk includes emissive light that is transmitted from a nanowell, through the passivation stack, and into a neighboring unassociated light guide and detected by an unassociated light detector. Crosstalk contributes to the noise level of the data signals that are processed from the light detectors and its associated device circuitry. Under some circumstances, for some ranges of pitches of nanowell rows (e.g., a range of about 1.5 microns or less, or a range of about 1.0 microns or less) crosstalk may become a dominating factor in noise contribution. In addition, nanowell size (diameter) is often reduced to accommodate tighter pitch. As a result, the total number of analytes in each nanowell (and consequently the total available emissive signal from each well) is reduced, further compounding the effect of noise such as crosstalk.
- Accordingly, there is a need to reduce crosstalk transmitted within an image sensor structure. More specifically, there is a need to reduce crosstalk of an image sensor structure that is transmitted from a nanowell, through the passivation stack of an image sensor structure, and into the top surfaces of light guides that are not associated with the nanowell. Additionally, there is a need to reduce such crosstalk transmitted through a passivation stack before it enters the light guides. Also, there is a need to reduce crosstalk of image sensor structures wherein the pitch between rows of nanowells is about 1.5 microns or less.
- The following clauses are included.
- 1. An image sensor structure, comprising:
- an image layer comprising an array of light detectors disposed therein;
- a device stack disposed over the image layer;
- an array of light guides disposed in the device stack, each light guide associated with at least one light detector of the array of light detectors;
- a passivation stack disposed over the device stack, comprising a first (1st) passivation layer and a 1st chemical protection layer disposed over the 1st passivation layer; and
- an array of nanowells, wherein the contours of the nanowells are formed by a top layer of the passivation stack, each nanowell associated with a light guide of the array of light guides,
- further comprising a crosstalk blocking metal structure disposed in the passivation stack, wherein the crosstalk blocking metal structure is configured to reduce crosstalk within the passivation stack.
- 2. The image sensor according to clause 1, wherein a bottom surface of the passivation stack is in direct contact with a top surface of the light guides; wherein the bottom surface of the passivation stack is preferably comprised in the 1st passivation layer of the passivation stack.
- 3. The image sensor structure of clause 1 or 2, wherein the crosstalk blocking metal structure comprises metal pillars disposed in the 1st passivation layer, and/or wherein the crosstalk blocking metal structure comprises parallel metal layers disposed in the 1st passivation layer.
- 4. The image sensor structure of any of the previous clauses, further comprising
- a second (2nd) passivation layer disposed over the 1st chemical protection layer; and
- a 2nd chemical protection layer disposed over the 2nd passivation layer;
- wherein the nanowells are disposed in a top layer of the 2nd chemical protection layer; wherein the crosstalk blocking metal structure preferably comprises parallel metal layers disposed in the 2nd passivation layer.
- 5. The image sensor structure of clause 4, wherein the 2nd passivation layer is composed of a silicon nitride (SiN) and/or wherein the 2nd chemical protection layer is composed of a tantalum pentoxide (Ta2O5).
- 6. The image sensor structure of clause 4 or 5, wherein the crosstalk blocking metal structure comprises metal pillars extending from a bottom surface of the 1st passivation layer to a top surface of the 2nd passivation layer, the metal pillars disposed between the nanowells.
- 7. The image sensor structure of any of the preceding clauses, wherein the crosstalk blocking metal structure is composed of one or more of a tantalum (Ta), a tungsten (W), an aluminum (Al) and a copper (Cu), wherein the 1st passivation layer is composed of a silicon nitride (SiN); and/or wherein the 1st chemical protection layer is composed of a tantalum pentoxide (Ta2O5).
- 8. The image sensor structure of any of the preceding clauses, further comprising a light shield layer disposed between the device stack and the passivation stack.
- 9. The image sensor structure of any of the preceding clauses, wherein the passivation layer comprises more than two layers.
- 10. The image sensor structure according to any of the preceding clauses, wherein the crosstalk blocking structure comprises at least one of metal pillars and parallel metal layers disposed between the nanowells.
- 11. A method, comprising:
- etching an array of light guide apertures into a device stack, the device stack disposed over an image layer, the image layer comprising an array of light detectors disposed therein;
- forming an array of light guides in the light guide apertures, each light guide associated with at least one light detector of the array of light detectors;
- disposing a passivation layer over the array of light guides, such that a bottom surface of the passivation layer is in direct contact with a top surface of the light guides and forming the contour of an array of nanowells in the passivation stack, each nanowell associated with a light guide of the array of light guides;
- disposing a chemical protection layer over the passivation layer; and
- disposing a crosstalk blocking metal structure within the passivation stack formed by at least the passivation layer and the chemical protection layer, wherein the crosstalk blocking metal structure reduces crosstalk within the passivation stack.
- 12. The method of clause 11, further comprising
recessing the light guides into the light guide apertures such that upper portions of inner side walls of the light guide apertures are exposed and the top surfaces of the light guides are recessed to a predetermined depth below a top opening of the light guide apertures; wherein disposing the passivation layer preferably comprises conforming the passivation layer to the upper portions of the inner walls of the light guide apertures to form the array of nanowells in the top layer of the passivation layer, each nanowell associated with a single light guide; and/or wherein disposing crosstalk blocking structures comprises disposing between the nanowells, metal pillars within the passivation layer; and/or wherein the method further comprises:- disposing a 2nd passivation layer over the chemical protection layer; and
- disposing a 2nd chemical protection layer over the 2nd passivation layer.
- 13. The method according to
clauses 11 or 12 for providing an image sensor structure according to any of clauses 1-10. - 14. An image sensor structure obtainable according to the method of
clauses 11 or 12. - 15. Use of an image sensor structure according to any of clauses 1-10 in a biological assay.
- The present disclosure offers advantages and alternatives over the prior art by providing an image sensor structure for example having crosstalk blocking metal structures disposed in the passivation stack. The crosstalk blocking metal structures may include pillars or parallel metal plates. By being disposed within the passivation structure, the crosstalk blocking metal structures significantly reduce crosstalk transmitted within the passivation layer and prior to entering top surfaces of light guides of the image sensor structure.
- An image sensor structure in accordance with one or more aspects of the present disclosure includes an image layer. The image layer includes an array of light detectors disposed therein. A device stack is disposed over the image layer. An array of light guides is disposed in the device stack. Each light guide is associated with at least one light detector of the array of light detectors. A passivation stack is disposed over the device stack, comprising a first passivation layer and a first chemical protection layer disposed over the first passivation layer. The passivation stack for example includes a bottom surface in direct contact with a top surface of the light guides. An array of nanowells is disposed in a top layer of the passivation stack, wherein the contours of the nanowells are formed by a top layer of the passivation stack. Each nanowell is associated with a light guide of the array of light guides. A crosstalk blocking metal structure is disposed in the passivation stack. The crosstalk blocking metal structure reduces crosstalk within the passivation stack.
- Another image sensor structure in accordance with one or more aspects of the present disclosure includes an image layer. The image layer includes an array of light detectors disposed therein. A device stack is disposed over the image layer. An array of light guides is disposed in the device stack. Each light guide is associated with at least one light detector of the array of light detectors. A passivation stack is disposed over the device stack. The passivation stack includes a 1st passivation layer having a bottom surface in direct contact with a top surface of the light guides. The passivation stack also includes a 1st chemical protection layer disposed over the 1st passivation layer. The passivation stack also includes a 2nd passivation layer disposed over the 1st chemical protection layer and a 2nd chemical protection layer disposed over the 2nd passivation layer. An array of nanowells is disposed in a top layer of the passivation stack. Each nanowell is associated with a light guide of the array of light guides.
- A method of forming an image sensor structure in accordance with one of more aspects of the present disclosure includes disposing a device stack over an image layer. The image layer includes an array of light detectors disposed therein. An array of light guide apertures is etched into the device stack. An array of light guides is formed in the light guide apertures. Each light guide is associated with at least one light detector of the array of light detectors. A 1st passivation layer is disposed over the array of light guides, such that a bottom surface of the 1st passivation layer is in direct contact with a top surface of the light guides. A 1st chemical protection layer is disposed over the 1st passivation layer. The 1st chemical protection layer and 1st passivation layer are included in a passivation stack.. An array of nanowells is formed in a top layer of the passivation stack, with the contours of the nanowells formed by the top layer of the passivation stack. Each nanowell is associated with a light guide of the array of light guides. A crosstalk blocking metal structure disposed within the passivation stack. The crosstalk blocking metal structure reduces crosstalk within the passivation stack.
- The disclosure will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
-
FIG. 1 is a simplified cross sectional side view of a sensor system having an image sensor structure disposed therein; -
FIG. 2 is a simplified cross sectional side view of an image sensor structure having crosstalk blocking metal structures in the form of pillars in a passivation stack in accordance with one example described herein; -
FIG. 3 is a simplified cross sectional side view of an image sensor structure having crosstalk blocking metal structures in the form of pillars in accordance with one example described herein; -
FIG. 4 is a simplified cross sectional side view of an image sensor structure having crosstalk blocking metal structures in the form of pillars in accordance with one example described herein; -
FIG. 5 is a simplified cross sectional side view of an image sensor structure having crosstalk blocking metal structures in the form of parallel metal layers in accordance with one example described herein; -
FIG. 6 is a simplified cross sectional side view of an image sensor structure at an intermediate stage of manufacture having light guide apertures disposed in a device stack in accordance with one example described herein; -
FIG. 7 is a simplified cross sectional side view of the image sensor structure ofFIG. 6 having a light guide layer disposed thereon in accordance with one example described herein; -
FIG. 8 is a simplified cross-sectional side view of the image sensor structure ofFIG. 7 , having the light guide layer planarized down to form light guides in accordance with one example described herein; -
FIG. 9 is a simplified cross sectional side view of the image sensor structure ofFIG. 8 having the light guided recessed below a top of the light guide apertures in accordance with one example described herein; -
FIG. 10 is a simplified cross sectional side view of the image sensor structure ofFIG. 9 having crosstalk blocking metal structures in the form of pillars in a passivation stack, the passivation stack being disposed over a top surface of the light guides to form a completed image sensor structure in accordance with one example described herein; -
FIG. 11 is a simplified cross sectional side view of an image sensor structure at an intermediate stage of manufacture having crosstalk blocking metal structures in the form of pillars in a partially formed passivation stack in accordance with one example described herein; -
FIG. 12 is a simplified cross sectional side view of the image sensor structure ofFIG. 11 having a fully formed passivation stack to form a completed image sensor structure in accordance with one example described herein; -
FIG. 13 is a simplified cross sectional side view of an image sensor structure at an intermediate stage of manufacture having crosstalk blocking metal structures in the form of pillars in a partially formed passivation stack in accordance with one example described herein; -
FIG. 14 is a simplified cross sectional side view of the image sensor structure ofFIG. 13 having a fully formed passivation stack to form a completed image sensor structure in accordance with one example described herein; -
FIG. 15 is a simplified cross sectional side view of an image sensor structure at an intermediate stage of manufacture having a partially formed passivation stack in accordance with one example described herein; and -
FIG. 16 is a simplified cross sectional side view of the image sensor structure ofFIG. 15 having crosstalk blocking metal structures in the form of parallel metal layers in a fully formed passivation stack to form a completed image sensor structure in accordance with one example described herein. - Certain examples will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the methods, systems, and devices disclosed herein. One or more examples are illustrated in the accompanying drawings. Those skilled in the art will understand that the methods, systems, and devices specifically described herein and illustrated in the accompanying drawings are non-limiting examples and that the scope of the present disclosure is defined solely by the claims. The features illustrated or described in connection with one example may be combined with the features of other examples. Such modifications and variations are intended to be included within the scope of the present disclosure.
- The terms "substantially", "approximately", "about", "relatively" or other such similar terms that may be used throughout this disclosure, including the claims, are used to describe and account for small fluctuations, such as due to variations in processing. For example, they can refer to less than or equal to ± 10%, such as less than or equal to ± 5%, such as less than or equal to ± 2%, such as less than or equal to ± 1%, such as less than or equal to ± 0.5%, such as less than or equal to ± 0.2%, such as less than or equal to ± 0.1%, such as less than or equal to ± 0.05%.
- Examples provided herein relate to image sensor structures and methods of making the same. More specifically, examples provided herein relate to image sensor structures having crosstalk blocking metal structures disposed within a passivation stack of the image sensor structures.
-
FIG. 1 illustrates a sensor system having one type of image sensor structure disposed therein.FIGS. 2-5 illustrate various examples of image sensor structures in accordance with the present disclosure.FIGS. 6-16 illustrate various examples of methods of making image sensor structures in accordance with the present disclosure. - Referring to
FIG. 1 , an example sensor system 10 (which, in this example, is a biosensor system 10) includes aflow cell 12 bonded to animage sensor structure 14. Theflow cell 12 of thebiosensor system 10 includes aflow cell cover 16 affixed to flowcell sidewalls 18. The flow cell sidewalls 18 are bonded to atop layer 22 of apassivation stack 24 of theimage sensor structure 14 to form aflow channel 20 therebetween. - The
top layer 22 of thepassivation stack 24 includes a large array ofnanowells 26 disposed thereon. Analytes 28 (such as DNA segments, oligonucleotides, other nucleic-acid chains or the like) may be disposed within thenanowells 26. The flow cell cover includes aninlet port 30 and anoutlet port 32 that are sized to allowfluid flow 34 into, through and out of theflow channels 20. Thefluid flow 34 may be utilized to perform a large number of various controlled reaction protocols on theanalytes 28 disposed within thenanowells 26. Thefluid flow 34 may also deliver an identifiable label 36 (such as a fluorescently labeled nucleotide molecule or the like) that can be used to tag theanalytes 28. - The
image sensor structure 14 of thebiosensor 10 includes animage layer 40 disposed over abase substrate 38. Theimage layer 38 may be a dielectric layer, such as SiN and may contain an array oflight detectors 42 disposed therein. Alight detector 42 as used herein may be, for example, a semiconductor, such as a photodiode, a complementary metal oxide semiconductor (CMOS) material, or both. Thelight detectors 42 detect light photons of emissive light 44 that is emitted from the fluorescent labels 36 attached to theanalytes 28 in thenanowells 26. Thebase substrate 38 may be glass, silicon or other like material. - A
device stack 46 is disposed over theimage layer 40. Thedevice stack 46 may contain a plurality of dielectric layers (not shown) that containvarious device circuitry 48 which interfaces with thelight detectors 42 and process data signals using the detected light photons. - Also disposed in the
device stack 46 is an array of light guides 50. Eachlight guide 50 is associated with at least onelight detector 42 of the array of light detectors. For example, thelight guide 50 may be located directly over its associated light detector. The light guides 50 direct photons of emissive light 44 from the fluorescent labels 36 on theanalytes 28 disposed in thenanowells 26 to their associatedlight detectors 42. - Also disposed within the
device stack 46, is alight shield layer 52, ananti-reflective layer 54 and aprotective liner layer 56. Theprotective liner layer 56, may be composed of a silicon nitride (SiN) and lines the inside walls of the light guides 50. Thelight shield layer 52, may be composed of tungsten (W) and attenuatesemissive light 44 andexcitation light 58 transmitted into thedevice stack 46. Theanti-reflective layer 54, may be composed of silicon oxynitride (SiON) and be used for photolithographic patterning of a metal layer underneath. - The
passivation stack 24 is disposed over thedevice stack 46. Thepassivation stack 24 includes abottom surface 60 that is in direct contact with atop surface 62 of the light guides 50. Thepassivation stack 24, may include apassivation layer 64 and a chemical protection layer 66 (which in this case is thetop layer 22 of the passivation stack 24). Thepassivation layer 64, may be composed of SiN and include thebottom surface 60 of thepassivation stack 24. Thechemical protection layer 66, may be composed of a tantalum pentoxide (Ta2O5) and may be thetop layer 22 of thepassivation stack 24. - The array of
nanowells 26 is also disposed in thetop layer 22 of thepassivation stack 24, wherein each nanowell 26 is associated with alight guide 50 of the array of light guides. For example, each nanowell 26 may be located directly above an associatedlight guide 50, such that most of the photons of emissive light 44 that enters thetop surface 62 of eachlight guide 50 is generated from within that light guide's associatednanowell 26. - During operation, various types of
excitation light 58 is radiated onto theanalytes 28 in thenanowells 26, causing the labeledmolecules 36 to fluoresceemissive light 44. The majority of photons of emissive light 44 may be transmitted through thepassivation stack 24 and enter thetop surface 62 of its associatelight guide 50. The light guides 50 may filter out most of theexcitation light 58 and direct theemissive light 44 to an associatedlight detector 42 located directly below thelight guide 50. - The
light detectors 42 detect the emissive light photons. Thedevice circuitry 48 within thedevice stack 46 then process and transmits data signal using those detected photons. The data signal may then be analyzed to reveal properties of the analytes. - However, some photons of emissive light from one nanowell may be inadvertently transmitted through the
passivation stack 24 to a neighboring unassociatedlight guide 50 to be detected as unwanted crosstalk in anunassociated light detector 42. This crosstalk contributes to noise in the data signals. - For
image sensor structures 14 having small pitches between rows of nanaowells (for example, nanowells with a pitch of about 1.5 microns or smaller, or more so with a pitch of about 1.25 microns or smaller, and even more so with a pitch of about 1 micron or smaller) such crosstalk may significantly increase noise levels associated with the data signals. In addition, nanowell size (diameter) is often reduced to accommodate tighter pitch. As a result, the total number of analytes in each nanowell (and consequently the total available emissive signal from each well) is reduced, further compounding the effect of noise such as crosstalk. Therefore, the more an image sensor structure is scaled down, the more desirable it becomes to reduce crosstalk that is transmitted within thepassivation stack 24. - The example sensor systems described herein differ from some pre-existing sensor systems in several aspects. For example, in one contrasting example, crosstalk shields (not shown) are disposed in its
device stack 46, which is located below itspassivation stack 24. In this contrasting example, the crosstalk shields are used to reduce crosstalk that leaks out of itslight guide 50 and is transmitted through itsdevice stack 46 to anotherlight guide 50. These crosstalk shields do not reduce crosstalk that is transmitted through itspassivation stack 24 and into thetop surface 62 of its light guides 50. The crosstalk shields of this contrasting example are different from the examples provided herein. - Referring to
FIG. 2 , a cross-sectional side view of an example of animage sensor structure 100 having crosstalk blocking metal structures 102 in apassivation stack 104 of theimage sensor structure 100 is illustrated. The crosstalk blocking metal structures 102 may be any appropriate shape, but in this example, they are in the form ofmetal pillars 106. The term "pillar", as used herein, includes structures that extend from a bottom surface to a top surface of a layer in a passivation stack. For example, themetal pillars 106 inFIG. 2 extend from thebottom surface 140 of the 1stpassivation layer 142 to a top surface of the 1stpassivation layer 142 withinpassivation stack 104. - The
image sensor structure 100 may be bonded to a flow cell to form a sensor system similar to that of thesensor system 10 inFIG. 1 . The sensor system may be, for example, a biosensor system. - The
image sensor structure 100 includes animage layer 108 disposed over abase substrate 110. Thebase substrate 110 may comprise glass or silicon. Theimage layer 108 may comprise a dielectric layer, such as SiN. - An array of
light detectors 112 is disposed within theimage layer 108. Alight detector 112 as used herein may be, for example, a semiconductor, such as a photodiode, a complementary metal oxide semiconductor (CMOS) material, or both. Thelight detectors 112 detect light photons of emissive light 114 that are emitted from fluorescent labels 116 attached toanalytes 118 innanowells 120 disposed in atop layer 122 of thepassivation stack 104. The fluorescent labels 116 are made to fluoresce by anexcitation light 124 during various controlled reaction protocols. - A
device stack 126 is disposed over the image layer. Thedevice stack 126 may contain a plurality of dielectric layers (not shown) that containvarious device circuitry 128 which interfaces with thelight detectors 112 and process data signals using the detected light photons of emissive light 114. - Also disposed in the
device stack 126 is an array of light guides 130. Eachlight guide 130 is associated with at least onelight detector 112 of the array of light detectors. For example, alight guide 130 may be located directly over its associated light detector112. The light guides 130 direct photons of emissive light 114 from the fluorescent labels 116 on theanalytes 118 disposed in thenanowells 120 to their associatedlight detectors 112. - In this example, also disposed within the
device stack 126, is alight shield layer 134, ananti-reflective layer 136 and aprotective liner layer 138. Theprotective liner layer 138, may be composed of a dielectric material, such as silicon nitride (SiN) or other similar materials, and lines the inside walls of the light guides 130. Thelight shield layer 134, may be composed of a transition material, such as tungsten (W) or other similar materials, and attenuates emissive light 114 andexcitation light 124 transmitted into thedevice stack 126. Theanti-reflective layer 136, may be composed of an anti-reflective compound, such as silicon oxynitride (SiON), or other similar materials and used for photolithographic patterning of a metal layer underneath. - The
passivation stack 104 is disposed over thedevice stack 126. Thepassivation stack 104 includes abottom surface 140 that is in direct contact with thetop surface 132 of the light guides 130. Thepassivation stack 104, may include any number of layers of material appropriate to transmit emissive light 114. However, in this example, thepassivation stack 104 includes a first (1st)passivation layer 142 and a 1stchemical protection layer 144. The 1stpassivation layer 142, may be composed of SiN and include thebottom surface 140 of thepassivation stack 104. The 1stchemical protection layer 144, may be composed of a transition metal oxide, such as tantalum pentoxide (Ta2O5) or other similar materials, and be thetop layer 122 of thepassivation stack 104. - An array of
nanowells 120 is also disposed in thetop layer 122 of thepassivation stack 104, wherein eachnanowell 120 is associated with alight guide 130 of the array of light guides. For example, eachnanowell 120 may be located directly above an associatedlight guide 130, such that most of the photons of emissive light 114 that enters thetop surface 132 of eachlight guide 130 is generated from within that light guide's associatednanowell 120. - The crosstalk blocking metal structures 102 are disposed in the
passivation stack 104, wherein the crosstalk blocking metal structures 102 may reduce crosstalk within thepassivation stack 104. The crosstalk blocking metal structures 102 may be any appropriate shape, but in this example, they are in the form ofmetal pillars 106. The crosstalk blocking metal structures 102 may be disposed in any appropriate location within thepassivation stack 104, but in this example, they are disposed solely in the 1stpassivation stack 142 and between the nanowells 120. The crosstalk blocking metal structure 102 may be composed of such metals as, for example, tantalum (Ta), tungsten (W), aluminum (Al) or copper (Cu). - The crosstalk blocking metal structures 102 may reduce crosstalk that is transmitted through the
passivation stack 104 by any appropriate process. For example, the crosstalk blocking metal structures 102 may be composed of a material that absorbs the emissive light or blocks the emissive light at a given emissive light frequency. Alternatively, the crosstalk blocking metal structures 102 may have a geometric shape and placement within thepassivation stack 104 that enables the crosstalk blocking metal structures 102 to direct emissive light 114 away from thetop surfaces 140 of the light guides 130. - During operation each
nanowell 120 receivesanalytes 118 that are tagged with a fluorescent molecular label 116, which generates emissive light 114 in response to anexcitation light 124. Photons of the emissive light 114 are transmitted from ananowell 120, through the passivation stack, and into thetop surface 140 of an associatedlight guide 130, which may be located directly below thenanowell 120. The photons of emissive light 114 are then guided by the associatedlight guide 130 to an associatedlight detector 112, which may be located directly below thelight guide 130. The associatedlight detectors 112 detect the photons of emissive light 114. Additionally,device circuitry 128 is integrated with thelight detectors 112 to process the detected emissive light photons and provide data signals using the detected emissive light photons. - Simultaneously with the processing of such data signals, the crosstalk blocking metal structures 102 may significantly reduce the number of photons of emissive light 114 that may become crosstalk. The reduction may be at least about 5% (e.g., at least about 20%, 30%, 40%, 50%, 60%, or more). In more examples, the reduction is between about 5% to about 50%, such as between 10% and 30%. Other values are also possible. In one example, the crosstalk blocking metal structures 102 reduce the number of emissive light photons that may otherwise be transmitted from a
nanowell 120 to an unassociated neighboringlight guide 130 and detected by an unassociatedlight detector 120 as crosstalk. Since such crosstalk may contribute to the noise level of the data signals, the noise level of the data signals is significantly reduced. - Referring to
FIG. 3 , a cross-sectional side view of another example of animage sensor structure 200 having crosstalk blocking metal structures 102 in the form of pillars 202 is illustrated. Theimage sensor structure 200 is similar toimage sensor structure 100 wherein like features have been labeled with like reference numbers. - The
passivation stack 104 ofimage sensor structure 200 includes four layers. Those four layers include: - The 1st
passivation layer 142 being disposed over the light guides 130. - The 1st
chemical protection layer 144 being disposed over the 1stpassivation layer 142. - A 2nd
passivation layer 204 being disposed over the 1stchemical protection layer 144. - A 2nd
chemical protection layer 206 being disposed over the 2ndpassivation layer 204. - The four
layers image sensor structure 200, and in subsequentimage sensor structures layers image sensor 100. Those advantages may include, without limitation: - The four layer passivation stack enables the deposition of larger and more geometrically complex crosstalk blocking metal structures, which may reduce crosstalk more effectively than the crosstalk blocking metal structures that can be disposed in a two layer passivation stack.
- The four layer passivation stack enables more flexibility in nanowell design since the nanowell geometry will be less constrained by the light guide structure underneath, due to the added layers.
- The four layer passivation stack provides more robustness from any chemical or mechanical damage, due to the increase of the passivation stack thickness as well as the added layer.
- In this example, the
bottom surface 140 of the 1stpassivation layer 142 is still the bottom surface of thepassivation stack 104 and is in direct contact with thetop surface 132 of the light guides 130. However, thetop layer 122 of thepassivation stack 104 is now the 2ndchemical protection layer 206. Additionally, thenanowells 120 are disposed in the 2ndchemical protection layer 206. - The composition of the 2nd
passivation layer 204 and 2ndchemical protection layer 206 may be the same as, or similar to, the composition of the 1stpassivation layer 142 and the 1stchemical protection layer 144 respectively. For example, the 2ndpassivation layer 204 may be composed of SiN and 2ndchemical protection layer 206, may be composed of a tantalum pentoxide (Ta2O5). - The crosstalk blocking metal structure 102 of
image sensor structure 200 includes the metal pillars 202. The metal pillars 202 are disposed in the 1stpassivation layer 104 and are located between the nanowells 120. - Referring to
FIG. 4 , a cross-sectional side view of another example of animage sensor structure 300 having crosstalk blocking metal structures 102 in the form of pillars 202 is illustrated. Theimage sensor structure 300 is similar toimage sensor structures - The
passivation stack 104 ofimage sensor structure 300 is the same as, or similar to, the passivation stack ofimage sensor structure 200 and also includes four layers. Those four layers include: - The 1st
passivation layer 142 being disposed over the light guides 130. - The 1st
chemical protection layer 144 being disposed over the 1stpassivation layer 142. - The 2nd
passivation layer 204 being disposed over the 1stchemical protection layer 144. - The 2nd
chemical protection layer 206 being disposed over the 2ndpassivation layer 204. - In this example, the
bottom surface 140 of the 1stpassivation layer 142 is still the bottom surface of thepassivation stack 104 and is in direct contact with thetop surface 132 of the light guides 130. Additionally, thetop layer 122 of thepassivation stack 104 is the 2ndchemical protection layer 206. Moreover, thenanowells 120 are disposed in the 2ndchemical protection layer 206. - However, the crosstalk blocking metal structure 102 of
image sensor structure 300 includes the metal pillars 302. The metal pillars 302 extend from thebottom surface 140 of the 1stpassivation layer 142 to atop surface 304 of the 2ndpassivation layer 204. The metal pillars are also disposed between the nanowells 120. - Referring to
FIG. 5 , a cross-sectional side view of another example of animage sensor structure 400 having crosstalk blocking metal structures 102 in the form of parallel metal layers 402 is illustrated. Theimage sensor structure 400 is similar toimage sensor structures - The
passivation stack 104 ofimage sensor structure 400 is the same as, or similar to, the passivation stack ofimage sensor structure - The 1st
passivation layer 142 being disposed over the light guides 130. - The 1st
chemical protection layer 144 being disposed over the 1stpassivation layer 142. - The 2nd
passivation layer 204 being disposed over the 1stchemical protection layer 144. - The 2nd
chemical protection layer 206 being disposed over the 2ndpassivation layer 204. - In this example, the
bottom surface 140 of the 1stpassivation layer 142 is still the bottom surface of thepassivation stack 104 and is in direct contact with thetop surface 132 of the light guides 130. Additionally, thetop layer 122 of thepassivation stack 104 is the 2ndchemical protection layer 206. Moreover, thenanowells 120 are disposed in the 2ndchemical protection layer 206. - However, the crosstalk blocking metal structure 102 of
image sensor structure 400 includes the parallel metal layers 402. In this example, the parallel metal layers 402 are disposed in the 2ndpassivation layer 204 and between the nanowells 120. However, the parallel metal layers 402 may be disposed in the 1stpassivation layer 142 and between thenanowells 120 as well. - The geometric shape and placement of the parallel metal layers 402 enable these particular crosstalk blocking metal structures 102 to direct crosstalk emissive light in a direction that is relatively parallel to the metal layers 402 and away from unassociated
light detectors 112. Additionally, the composition of the parallel metal layers 402 enables these particular crosstalk blocking metal structures 102 to absorb such crosstalk emissive light. - Referring to
FIGS. 6-15 , the following figures illustrate various methods of making theimage sensor structures - Referring to
FIG. 6 , a cross sectional side view of an example ofimage sensor structure 100 at an intermediate stage of manufacture is illustrated. At this stage of the process flow, theimage layer 108 is disposed over thebase substrate 110. The image layer includes the array oflight detectors 112 disposed therein. Theimage layer 108 can be disposed over thebase substrate 110 using deposition techniques, such as chemical vapor deposition (CVD) or physical vapor deposition (PVD). - The multiple dielectric layers (not shown) of the
device stack 126, with its associated device circuitry, can also be disposed over theimage layer 108 using deposition techniques. Thelight shield layer 134 and theanti-reflective layer 136 may thereafter be disposed over thedevice stack 126 using any suitable deposition techniques, such as CVD, PVD, atomic layer deposition (ALD) or electro-plating. - Thereafter in the process flow, an array of
light guide apertures 150 are etched into the device stack. This may be done using any suitable etching processes, such as an anisotropic etching process, such as reactive ion etching (RIE). An etching process in this disclosure may include patterning, such as lithographic patterning. - The
protective liner layer 136 can then be disposed over the entireimage sensor structure 100, including thesidewalls 152 andbottom 154 of theapertures 150. This may be done using any suitable deposition techniques, such as CVD, PVD or ALD. - Referring to
FIG. 7 , thereafter in the process flow, alight guide layer 156 is disposed over theentire structure 100 to fill theapertures 150. The light guide layer may be composed of an organic filter material that is capable of filtering out the known wavelengths ofexcitation light 124 and transmitting through known wavelengths of emissive light 114. Thelight guide layer 156 may be composed of custom formulated dye molecules arranged in a high index polymer matrix. - Referring to
FIG. 8 , thelight guide layer 156 is thereafter planarized down to form the light guides 130, wherein thetop surfaces 132 of the light guides 130 are substantially level with the top surface of theprotective liner layer 138. This may be done using any suitable polishing technique, such as a chemical mechanical polishing (CMP) process. Once polished down, the overall top surface of theimage sensor structure 100 is substantially flat. - Referring to
FIG. 9 , the light guides 130 are thereafter recessed down into thelight guide apertures 150, wherein eachlight guide 130 is associated with at least onelight detector 112 of the array of light detectors. This can be done with a timed etching process that recesses thelight guide layer 156 down at a given rate for a known amount of time. - When the etching process is finished, the light guides 130 have been recessed into the
light guide apertures 150 such thatupper portions 158 ofinner side walls 152 of thelight guide apertures 150 are exposed. Additionally, thetop surfaces 132 of the light guides 130 are recessed to a predetermined depth below atop opening 160 of thelight guide apertures 150. - Referring to
FIG. 10 , thereafter the 1stpassivation layer 142 is disposed over the array of light guides 130, such that thebottom surface 140 of the 1stpassivation layer 142 is in direct contact with thetop surface 132 of the light guides 130. The 1stchemical protection layer 144 can then be disposed over the 1stpassivation layer 142. Both of these processes may be done by CVD or PVD. The 1stchemical protection layer 144 and 1stpassivation layer 142 form at least a portion of thepassivation stack 104. - The array of
nanowells 120 may be formed in thetop layer 122 of thepassivation stack 104 at an appropriate point in the process flow. Eachnanowell 120 is associated with alight guide 130 of the array of light guides. - For the specific example of
image sensor structure 100 as illustrated inFIG. 10 , thenanowells 120 may be formed by disposing the 1stpassivation layer 142 such that it conforms to theupper portions 158 of theinner side walls 152 of thelight guide apertures 150. This may be done by CVD, PVD or ALD. Accordingly, the contour of the 1stpassivation layer 142 forms the array ofnanowells 120 in the 1st passivation layer such that each nanowell is associated, and selfaligned, with a singlelight guide 130. - Additionally, the crosstalk blocking metal structures 102 can be disposed within the
passivation stack 104 at an appropriate point in the process flow. Each crosstalk blocking metal structure 102 may reduce crosstalk within thepassivation stack 104. - For the specific example of
image sensor structure 100 as illustrated inFIG. 10 , the crosstalk blocking structures may be formed asmetal pillars 106 by lithographicallyetching pillar cavities 162 into the 1stpassivation layer 142 such that thepillar cavities 162 are disposed between the nanowells 120. This may be done by a RIE process. - The
metal pillars 106 may then be disposed within the pillar cavities 162. This may be done by a metal plating process. Later any overflow caused by the plating process may be removed by a chemical mechanical polishing (CMP) process. - After deposition of the 1st
passivation layer 142 and the formation of themetal pillars 106, the 1stchemical protection layer 144 may be disposed over the 1stpassivation layer 142 to complete the formation ofimage sensor structure 100. The 1stchemical protection layer 144 may be disposed using CVD, PVD or ALD. - Referring to
FIG. 11 , a cross sectional side view of an example ofimage sensor structure 200 at an intermediate stage of manufacture is illustrated. This example of the process flow ofimage sensor structure 200 is the same as, or similar to, the example of the process flow ofimage sensor 100 up to and including the process flow disclosed with regards toFIG. 8 . Therefore, at this stage of the process flow, thetop surface 132 of the light guides 130 are substantially level with the top surface of theprotective liner layer 138. Therefore, the overall top surface of theimage sensor structure 200 is substantially flat. - Thereafter, the 1st
passivation layer 142 is disposed over thestructure 200, such that thebottom surface 140 of the 1stpassivation layer 142 is in direct contact with thetop surface 132 of the light guides 130. This 1stpassivation layer 142 ofstructure 200 provides a substantially levelupper surface 208 of the 1stpassivation layer 142. This may be done by CVD or PVD. - The metal pillars 202 (which are the crosstalk blocking metal structures 102 in this example) may then be disposed into the 1st
passivation layer 142. This can be done by firstetching pillar cavities 210 into the 1stpassivation layer 142. This may be done using a RIE process. The metal pillars 202 may then be disposed within thepillar cavities 210 using CVD, PVD or electro-plating. Any overflow caused by the deposition of the metal pillars 202 into thepillar cavities 210 may later be removed by a chemical mechanical polishing (CMP) process. - Thereafter, the 1st
chemical protection layer 144 may be disposed over the relatively flatupper surface 208 of the 1stpassivation layer 142. This may be done by CVD, PVD or ALD. - Referring to
FIG. 12 , thereafter in the process flow, the 2ndpassivation layer 204 is disposed over the 1stchemical protection layer 144. This may be done using any suitable deposition technique, such as CVD, PVD or ALD. -
Nanowells 120 can then be formed into the 2ndpassivation layer 204. This can be done by lithographically patterning and etching thenanowells 120 into the 2ndpassivation layer 204. - Thereafter the 2nd
chemical protection layer 206 is disposed over the 2ndpassivation layer 204 to complete the formation of theimage sensor structure 200. This may be done by using any suitable deposition technique, such as CVD, PVD or ALD. The deposition process conforms the 2ndchemical protection layer 206 to the contours of thenanowells 120 in the 2ndpassivation layer 204, therefore forming thenanowells 120 in the 2ndchemical protection layer 206. The 2ndchemical protection layer 206, the 2ndpassivation layer 204, the 1stchemical protection layer 144 and the 1stpassivation layer 142 are all included in thepassivation stack 104 of theimage sensor structure 200. - Referring to
FIG. 13 , a cross sectional side view of an example ofimage sensor structure 300 at an intermediate stage of manufacture is illustrated. This example of the process flow ofimage sensor structure 300 is the same as, or similar to, the example of the process flow ofimage sensor 100 up to and including the process flow disclosed with regards toFIG. 8 . Therefore, at this stage of the process flow, thetop surface 132 of the light guides 130 are at least substantially level with the top surface of theprotective liner layer 138. Therefore, the overall top surface of theimage sensor structure 300 is substantially flat. - Thereafter, the 1st
passivation layer 142 is disposed over thestructure 300, such that thebottom surface 140 of the 1stpassivation layer 142 is in direct contact with thetop surface 132 of the light guides 130. This 1stpassivation layer 142 ofstructure 300 provides a substantially levelupper surface 208 of the 1stpassivation layer 142. This may be done by any suitable deposition technique, such as CVD or PVD. - Thereafter, the 1st
chemical protection layer 144 may be disposed over the relatively flatupper surface 208 of the 1stpassivation layer 142. Then the 2ndpassivation layer 204 may be disposed over the 1stchemical protection layer 144. Both of theselayers - The metal pillars 302 (which are the crosstalk blocking metal structures 102 of image sensor structure 300) may then be disposed into the 2nd
passivation layer 204, the 1stchemical protection layer 144 and the 1stpassivation layer 142. This can be done by firstetching pillar cavities 306 into the 1st and 2nd passivation layers 142, 204 and into the 1stchemical protection layer 144. This may be done using a RIE process. The metal pillars 302 may then be disposed within thepillar cavities 306 using any suitable deposition technique, such as CVD, PVD or electro-plating. Any overflow caused by the deposition of the metal pillars 302 into thepillar cavities 306 may later be removed by any suitable polishing technique, such as a chemical mechanical polishing (CMP) process. - Referring to
FIG. 14 , thereafter nanowells 120 can then be formed into the 2ndpassivation layer 204. This can be done by lithographically patterning and etching thenanowells 120 into the 2ndpassivation layer 204. - Thereafter the 2nd
chemical protection layer 206 is disposed over the 2ndpassivation layer 204 to complete the formation of theimage sensor structure 300. This may be done by CVD, PVD or ALD. The deposition process conforms the 2ndchemical protection layer 206 to the contours of thenanowells 120 in the 2ndpassivation layer 204, therefore forming thenanowells 120 in the 2ndchemical protection layer 206. The 2ndchemical protection layer 206, the 2ndpassivation layer 204, the 1stchemical protection layer 144 and the 1stpassivation layer 142 are all included in thepassivation stack 104 of theimage sensor structure 300. - Referring to
FIG. 15 , a cross sectional side view of an example ofimage sensor structure 400 at an intermediate stage of manufacture is illustrated. This example of the process flow ofimage sensor structure 400 is the same as, or similar to, the example of the process flow ofimage sensor 100 up to and including the process flow disclosed with regards toFIG. 8 . Therefore, at this stage of the process flow, thetop surface 132 of the light guides 130 are substantially level with the top surface of theprotective liner layer 138. Therefore, the overall top surface of theimage sensor structure 400 is substantially flat. - Thereafter, the 1st
passivation layer 142 is disposed over thestructure 400, such that thebottom surface 140 of the 1stpassivation layer 142 is in direct contact with thetop surface 132 of the light guides 130. This 1stpassivation layer 142 ofstructure 400 provides a substantially levelupper surface 208 of the 1stpassivation layer 142. This may be done by using any suitable deposition technique, such as CVD or PVD. - Thereafter, the 1st
chemical protection layer 144 may be disposed over the relatively flatupper surface 208 of the 1stpassivation layer 142. This may be done by using any suitable deposition technique, such as CVD, PVD or ALD. - Referring to
FIG. 16 , thereafter a firstparallel metal layer 402A (which is one of the crosstalk blocking metal structures 102 of the image sensor structure 400) may be disposed over the 1stchemical protection layer 144.Metal layer 402A may be disposed by using any suitable deposition technique, such as CVD, PVD, ALD or electro-plating. - Then the 2nd
passivation layer 204 may be disposed over thefirst metal layer 402A. This may be done by using any suitable deposition technique, such as CVC or PVD. - Then a second
parallel metal layer 402B may be disposed over the 2ndpassivation layer 204 such that it is parallel to the firstparallel metal layer 402A. This may be done by using any suitable deposition technique, such as CVD, PVD, ALD or electro-plating. - Thereafter nanowells 120 can then be formed into the 2nd
passivation layer 204, and into theparallel metal layers nanowells 120 into the 2ndpassivation layer 204 and theparallel metal layers - Thereafter the 2nd
chemical protection layer 206 is disposed over the 2ndpassivation layer 204 to complete the formation of theimage sensor structure 400. This may be done by using any suitable deposition technique, such as CVD, PVD or ALD. The deposition process conforms the 2ndchemical protection layer 206 to the contours of thenanowells 120 in the 2ndpassivation layer 204, therefore forming thenanowells 120 in the 2ndchemical protection layer 206. The 2ndchemical protection layer 206, the 2ndpassivation layer 204, the 1stchemical protection layer 144 and the 1stpassivation layer 142 are all included in thepassivation stack 104 of theimage sensor structure 400. - Thereafter, the
image sensor structures image sensor structures - It should be appreciated that all combinations of the foregoing concepts (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the inventive subject matter disclosed herein.
- Although the foregoing examples have been described by reference to specific examples, it should be understood that numerous changes may be made within the scope of the inventive concepts described. Accordingly, it is intended that the examples should not be interpreted such as to limit the scope defined by the language of the following claims.
Claims (15)
- An image sensor structure, comprising:an image layer comprising an array of light detectors disposed therein;a device stack disposed over the image layer;an array of light guides disposed in the device stack, each light guide associated with at least one light detector of the array of light detectors;a passivation stack disposed over the device stack, the passivation stack comprising a bottom surface in direct contact with a top surface of the light guides;an array of nanowells disposed in a top layer of the passivation stack, each nanowell associated with a light guide of the array of light guides; anda crosstalk blocking metal structure disposed in the passivation stack, wherein the crosstalk blocking metal structure extends from at least a top surface of a layer in the passivation stack, wherein the crosstalk blocking metal structure reduces crosstalk within the passivation stack.
- The image sensor structure of claim 1,
wherein the passivation stack comprises a plurality of layers, the plurality of layers comprising a first (1st) passivation layer disposed over the light guides and a 1st chemical protection layer disposed over the 1st passivation layer. - The image sensor structure of claim 2, wherein the plurality of layers further comprises:a second (2nd) passivation layer disposed over the 1st chemical protection layer; anda 2nd chemical protection layer disposed over the 2nd passivation layer;wherein the nanowells are disposed in a top layer of the 2nd chemical protection layer.
- The image sensor structure of claims 2 or 3, wherein the 1st passivation layer is composed of a silicon nitride (SiN) and the 1st chemical protection layer is composed of a tantalum pentoxide (Ta2O5).
- The image sensor structure of any of claims 2 - 4, wherein the 2nd passivation layer is composed of a silicon nitride (SiN) and the 2nd chemical protection layer is composed of a tantalum pentoxide (Ta2O5).
- The image sensor structure of any of claims 1 - 5, wherein the crosstalk blocking metal structure extends from at least a bottom surface to the top surface of the top surface of the layer in the passivation stack.
- The image sensor structure of any of claims 1 - 6, wherein the crosstalk blocking metal structure is composed of one of a tantalum (Ta), a tungsten (W), an aluminum (Al) and a copper (Cu).
- The image sensor structure of any of claims 1 - 7, comprising a light shield layer disposed between the device stack and the passivation stack.
- An image sensor structure, comprising:an image layer comprising an array of light detectors disposed therein;a device stack disposed over the image layer;an array of light guides disposed in the device stack, each light guide associated with at least one light detector of the array of light detectors;a passivation stack disposed over the device stack, the passivation stack comprising:a 1st passivation layer comprising a bottom surface in direct contact with a top surface of the light guides,a 1st chemical protection layer disposed over the 1st passivation layer,a 2nd passivation layer disposed over the 1st chemical protection layer, anda 2nd chemical protection layer disposed over the 2nd passivation layer;an array of nanowells disposed in a top layer of the passivation stack, each nanowell associated with a light guide of the array of light guides; anda crosstalk blocking metal structure disposed in the passivation stack, wherein the crosstalk blocking metal structure reduces crosstalk in the passivation stack, wherein the crosstalk blocking structure extends from the bottom surface of the 1st passivation layer to a top surface of the 1st passivation layer.
- The image sensor structure of claim 9, wherein the crosstalk blocking structure extends from the bottom surface of the 1st passivation layer to a top surface of the 2nd passivation layer.
- A method, comprising:disposing a passivation layer over an array of light guides such that a bottom surface of the passivation layer is in direct contact with a top surface of the light guides, where each light guide of the array of light guides is associated with at least one light detector of an array of light detectors;disposing a chemical protection layer over the passivation layer, the chemical protection layer and passivation layer comprising at least a portion of a passivation stack; anddisposing a crosstalk blocking metal structure within the passivation stack, wherein the crosstalk blocking metal structure reduces crosstalk within the passivation stack.
- The method of claim 11, wherein the crosstalk blocking metal structure extends from at least a top surface of the passivation layer in the passivation stack.
- The method of claim 11, wherein the crosstalk blocking metal structure extends from at least a bottom surface to a top surface of the passivation layer in the passivation stack,
- The method of claim 11, wherein the crosstalk blocking metal structure comprises parallel metal layers.
- The method of claim 14, wherein the parallel metal layers have a width that is one half a wavelength of the crosstalk or greater.
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